This invention related to an electronic musical instrument having a control for automatically generating notes in predetermined relationships to notes selected by an organist.
Electronic organs have been known in which accompaniment notes played are transposed to the octave below the highest solo note in order to simulate harmony notes. Early attempts to implement such a feature have interconnected large numbers of switches activated by the solo and accompaniment keyboards in order to automatically provide a simple harmony in which the harmony notes are a function of the solo notes and accompaniment notes played. As digital techniques came into use, electronic harmony generators were developed to replace the complex interconnected switching networks. For example, a pulse train of time-encoded notes has been passed through a window so as to create harmony notes having the same note names as the actuated accompaniment notes. In other circuits, the accompaniment notes have been encoded, using a read only memory or ROM, into binary representations which then control a similar window for passing time-encoded notes representing note frequencies.
Some attempts have been made to produce harmony effects other than "closed harmony" in which the accompaniment notes are transposed to the octave below the highest solo note. For example, prewired circuits have passed accompaniment notes in the second octave below the highest solo note in an attempt to create "open harmony". However, the effect is not musically pleasing in that all of the notes are sounded in only one octave location.
Arpeggio generation is another type of automatic control for generating notes, which sound in the solo voice, in accordance with note names selected by an organist on an accompaniment keyboard. To allow a semi-automatic operation, it has been known to provide a shortened arpeggio keyboard which has been prewired to represent groups of notes so that, as an organist moves his finger across the keyboard, the same note names as actuated on the accompaniment keyboard will be sounded through several octaves. However, such arrangements limit the notes which can be played and sometimes create undesirable time gaps between notes so that a pleasing arpeggio effect is not produced.
Automatic note generators have included a fold back circuit in order to fold back all notes which fall outside the range of the organ, such as may occur when notes are automatically transposed. However, such a fold back of all notes creates a predictable response, and may produce notes in discord with other notes played by the organist.
Automatic note generators of the above type have involved digital integrated circuits which generally rely on time domain multiplexing in which each key is represented by an individual pulse within a string of pulse locations representing all octaves of the organ. Such an arrangement makes it difficult to manipulate notes in complex ways so as to produce a variety of musical effects.